Lamp arrangement

ABSTRACT

A directed beam of intense light radiation is produced from a lamp arrangement having a vapor tube light source producing relatively less intense omnidirectional light radiation and having coaxial tubular walls with the inner tubular wall defining an axial region where the light is concentrated by a reflector surrounding the outer tubular wall. The concentrated light radiation is collected and transformed into a beam of greater intensity by a cylindrical light-transparent member located in the axial region and having reflector means on one end for causing the light to pass through the other end. The lighttransparent member is spaced-apart from the inner wall of the light source and has an index of light refraction greater than a medium in the surrounding space so as to enable light passing through the transparent member to be reflected internally at the cylindrical surface of the member. To provide substantially total internal reflection of light entering the transparent member normal to the axis thereof, the reflector means includes a conical portion extending axially inside the cylindrical transparent member, with an angle of revolution about the axis substantially equal to half the critical angle for total internal reflection inside the light-transparent member.

United States Patent [191 Dank [in 3,775,609 [451 Nov. 27, 1973 LAMP ARRANGEMENT [75] Inventor: Milton Dank, Wyncote, Pa.

[73] Assignee: Litton Business Systems, Inc., New

York, N.Y.

[22] Filed: Aug. 7, 1972 [21] Appl. No.: 278,421

[52] US. Cl 240/4l.35 C, 240/1 EL, 240/41, 240/51.12, 313/113, 350/96 R [51] Int. Cl. F2lr 7/00 [58] Field of Search 240/41.35 R, 41.35 C, 240/41 R, 41.1, 41.37, 1 EL, 51.12; 350/96 R; 313/113 [56] References Cited UNITED STATES PATENTS 3,453,425 7/1969 Whitaker 240/41.35 R 1,857,120 5/1932 Transom 240/1 1.4 R 2,314,096 3/1943 Leverenz 240/41 R 2,681,977 6/1954 Ballard 313/113 X Primary Examiner-Richard L. Moses Attorney-Joseph R. Spalla et a1.

[57] ABSTRACT A directed beam of intense light radiation is produced from a lamp arrangement having a vapor tube light source producing relatively less intense omnidirecwhere the light is concentrated by a reflector sur rounding the outer tubular wall. The concentrated light radiation is collected and transformed into a beam of greater intensity by a cylindrical lighttransparent member located in the axial region and having reflector means on one end for causing the light to pass through the other end. The lighttransparent member is spaced-apart from the inner wall of the light source and has an index of light refraction greater than a medium in the surrounding space so as to enable light passing through the transparent member to be reflected internally at the cylindrical-surface of the member. To provide substantially total internal reflection of light entering the transparent member normal to the axis thereof, the reflector means includes a conical portion extending axially inside the cylindrical transparent member, with an angle of revolution about the axis substantially equal to half the critical angle for total internal reflection inside the light-transparent member.

15 Claims, 2 Drawing Figures p /3& 35 .231) 27 f 1 LAMP ARRANGEMENT BACKGROUND OF THEINVENTION This invention relates to a lamp arrangement for producing anarrow beam of intense light radiation from a relatively large light source rediating light omnidirectionally with less intensity, and more particularly to a lamp arrangement which is suitable for use in a printing system in which pulses of light radiation are directed onto an ink carrier for converting volatile materials within the ink into a propellant gas of high temperature and high pressure which, upon expanding, drives unheated and unvaporized ink from the ink carrier and through air for impacting onto a recording medium.

To vaporize the ink in a manner which will create a propelling force sufficient to drive the ink from the ink carrier, it is necessary to use pulses of light radiation having both a high energy level and a short duration. The pulses of light radiation must be sufficiently short to prevent the heat energy due to absorption of light from being dissipated by the ink carrier, for example by thermal conduction, and yet the light pulses must have a sufficiently high energy level to concentrate enough energy during the short time duration of the pulse so as to create a propellant gas of sufficient pressure to shear a portion of unheated ink from the ink carrier.

in the past, the only known source of light radiation capable of producing concentrated pulses of light having sufficient intensity and short duration for use in the above type of printing system has been a Q-switched laser. However, at the present time lasers are too expensive and physically too large for use in a desirably compact and inexpensive printing system of the type described. Other sources of relatively high intensity light radiation have been impractical because of the difficulty in concentrating light radiation into a narrow beam of sufficient intensity.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a lamp arrangement utilizing a relatively inexpensive light source and yet producing a beam of sufficient intensity suitable for use in a printing system in which light energy is used in causing ink to be propelled from an ink carrier and through air to a recording medium.

Another object of the invention is to provide a compact lamp arrangement for producing a narrow beam of intense light radiation sufficient for use in causing ink to be propelled from an ink carrier by utilizing a physically larger light source radiating light of relatively less intensity.

Still other objects, features and advantages of the present invention will become apparent to those skilled in the art from a reading of the following detailed description of the invention, taken in conjunction with the accompanying drawing, wherein:

FIG. 1 is a partial perspective view of a lamp arrangement constructed according to the present invention; and

FIG. 2 is a sectional side view of the lamp arrangesity. The light radiated by the'light source 13 is concentrated into a confined region, generally indicated at ]"5, where it is then collected into a beam of intense radiation in a manner to be described below by a lighttransparent member 17 having an elongated configuration with reflector means, generally indicated 19, blocking the passage of light through a rearward end 17b of the member 17 and causing it to pass through an opposite forward end 17a.

As shown, the light source 13 is in the form of a vapor tube in which a gaseous medium, suitable for producing light while conducting electricity, is contained between inner and outer tubular walls, 21, 23'respectively, with the opposite ends thereof, 21a, 23a and 21b, 23b respectively, suitably sealed to the ring-shaped electrodes 25, 27 respectively. The tubular walls 21, 23 and the electrodes 25, 27 are coaxially aligned about a common axis with the inner wall 21 forming a central axial opening throughout the length of the lamp arrangement 1 l which defines the confined region 15 for concentrating the light radiation. To concentrate the light radiation from the light source 13 into the cintral axial region 15, the outer tubular wall member 23 is surrounded with an exterior light reflector 29 having a cylindrical shape and extending substantially the entire length of the tubular wall 23 so that light radiated outwardly is reflected inwardly toward the central region 15. The number of parts forming the lamp arrangement 11 is reduced by forming the exterior light reflector 29 integrally with the electrode 27, and the electrodes 25, 27 may be electrically insulated from each other by a suitable insulator 31. in the form of a ring surrounding the outer tubularwall 23. n

The gaseous medium used in the light source 13 may be any of the gases commonly used to fill conventional high intensity electronicflash tubes, for example xenon, mercury, xenon and mercury combined, argon or other rare gases. The use of xenon is preferred because the efficiency of light output for electrical energy input has been found to be greater than any of the other conventional gases. The inner and outer tubular wall members 21, 23 respectively, may be constructed from a suitable light transmissive material, for example quartz, and the electrodes 25, 27 at the opposite ends of the coaxial tubes 21, 23 may be constructed from any suitable electrically conductive material, for example aluminum. The exterior cylindrical reflector 29 may also be constructed from aluminum with the inner surface polished to a high finish to maximize or specularly reflect the light toward the central region 15. The insulator 31 may be constructed from a suitable electrically insulating material, for example nylon.

As previously mentioned, the light concentrated throughout the confined region 15 is collected into a beam of more intense light radiation by means of an elongated light-transparent member 17. The collection of light in the transparent member 17 is accomplished by providing the member 17 with an index of refraction greater than a surrounding medium so that a portion of the light passing through the light-transparent member 17 will be internally reflected at thesurface of the member 17 interfacing with the surrounding medium. As shown, the lighttransparent member 17 is cylindrically shaped and supported in the central region 15 in coaxial relation with the inner tubular wall member 21 by means of ring-shaped spacers 33a, 33b which are on the opposite ends 17a, 17b respectively, of the member 17 and in contact with the electrodes 25, 27 respectively. The spacers 33a, 33b provide a cylindrical gap, generally indicated at 35, between the light source 13 and the light transparent member 17 and extending substantially the entire length of the cylinder 17. The gap 35 may be filled with air or any other suitable light transmissive medium, or even evacuated, so as to expose the cylindrical surface 170 of the member 17 to a medium having a lower index of refraction. Accordingly, a portion of the light entering the transparent member 17 will be contained inside the member 17 by internal reflection at the interfacing cylindrical surface 17c, and the reflector means 19 will reflect light passing toward the rearward end 17b and cause the light to pass through the forward end 170 as a beam of more intense radiation than that produced by the light source 13.

The light transparent member 17 may be formed from a number of suitable glasses, such as the boric acid base lanthanum glasses. Alternatively, the light transparent member 17 may be constructed from any suitable plastic having a high index of refraction, a surface which may be polished to a high finish and which will withstand continued irradiation without changing its transmissivity. The reflector means 19 for blocking the passage of light through the rearward end 17b of the transparent member 17 so as to pass the light through the opposite end 17a is shown as a specular light reflector covering the rearward surface of the transparent member 17 and which may desirably be in the form of a metallic coating, for example plated with silver. The ring-shaped spacers 33a, 33b may be constructed from a suitable material, for example nylon, and the surface portions facing toward the gap may be coated with a suitable reflective material, for example silver, to increase the light directed onto the member 17.

To maximize the intensity of the beam of light produced by the lamp arrangement 11, it is desirable to collect in the member 17 as much as possible of the light radiation concentrated into the confined region 15. Since the cylindrical light reflector 29 causes most of the light to be radiated into the confined region at an angle normal to the common axis of the lamp arrangement 11, the amount of light collected by the member 17 may be optimized by ensuring that substantially all of the incoming light radiated normal to the common axis is internally reflected inside the light transparent member 17. However, as is known, light radiation passing through two different refractive medias at an angle normal to the interfacing surfaces will not be reflected nor even refracted as it passes from one medium to another medium. Instead, to achieve refraction or reflection of the light at the interfacing surface, the light must be incident thereon at an angle from the normal to the surface, and to achieve total internal reflection the light must be incident on the surface at an angle from the normal which is equal to or greater than a critical angle determined by the refractive indexes of the adjacent medias. Accordingly, if the light radiation entering the confined region 15 at an angle normal to the common axis is to be collected into the resulting light beam, the member 17 must be constructed in such a manner as to ensure the reflection of this light radiation inside the member 17, since otherwise this light radiation will pass through the member 17 without even being refracted.

In accordance with the present invention, the light radiation collected inside the member 17 is maximized by modifying the member 17 to provide a reflective surface inside the transparent member 17 for reflecting the incoming light radiation normal to the common axis 'and directing it toward the interfacing cylindrical surface 17c at an angle of incidence equal to or greater than a critical angle for total internal reflection. As shown, the cylindrical member 17 is provided with a substantially conical recess 37 extending longitudinally in the member 17 in alignment with the common axis and with the apex adjacent the forward end 17a, and contiguous with the recess 37 is a substantially conical reflector 39, which forms a portion of the light reflecting means 19. Accordingly, the light in the confined region 15 which is radiated normal to the common axis will be reflected back toward the interfacing cylindrical surface instead of passing directly through the transparent member 17.

As previously mentioned, to maximize the amount of light collected by the member 17, the light radiation must be totally reflected inside the transparent member 17 at the interfacing cylindrical surface 17c and for this to occur the light radiation must be incident on the interfacing surface 17c at an angle, relative to normal, which is equal to or greater than a critical angle for total internal reflection. As is known, the critical angle for total internal reflection at an interfacing surface between two different refractive medias is a function of the ratio of the refractive indexes and may be determined from the formula:

sine 6 N N where N, is the index of refraction of the light transparent member 17, and N is the index of refraction of the medium in the gap 35.

To reflect the incoming light radiation normal to the common axis toward the interfacing surface 17c at an angle equal to or greater than critical angle 0 the conical reflector must have an angle at the apex which is equal to or greater than the previously determined critical angle 6 Since the configuration 'of the conical recess 37, and hence the conical reflector 39, may be defined as substantially equal to that generated by the revolution of a hypotenuse of a right triangle about the common axis with one of the sides of the triangle being parallel to the common axis, the angle between the hypotenuse and the side of the triangle which is parallel or congruent with the common axis must also be equal to or greater than half the critical angle.

In a preferred embodiment of the invention, the critical angle has been determined as approximately 34, based upon a refractive index of 1.75 for the light transparent member 17 and a refractive index of 10003 for air in the gap 35. Thus, the half angle of the conical reflector 39 is approximately 17. The conical recess 37 may be formed in the member 17 by drilling and polishing of the glass member 17, and the conical reflector 39 may be suitably formed by silver-plating the conical recess 37. For a plastic member 17, a silver-plated cone could be molded directly.

Although the reflective means 39 is shown as having a substantially conical configuration, other alternative embodiments could be used, for example a frustoconical reflector. Furthermore, in accordance with the teachings of the invention, the reflector means 19 could be formed by providing the conical recess 37 with a larger half angle such that the normally radiated light would be total internally reflected at the surface of conical recess 37, and also totally internally reflected at the interfacing cylindrical surface without the need for a reflective coating on the conical recess 37. However, this would also necessitate the use of a cylinder having greater diameter to width ratio and result in a less intense or larger diameter beam. Furthermore, although the light transparent member 17 is shown as being constructed from a solid material, it could also be constructed in the form of an envelope filled with a suitable light transparent fluid having a greater index of I refraction than the surrounding medium in'the gap 35.

From the above disclosure and teachings of the invention, it will be apparent to those skilled in the art that various modifications and improvements may be made. Accordingly, the scope of the invention is not to be limited by the illustrative embodiment, but only by the scope and spirit of the apended claims.

What is claimed is:

1. ln a lamp arrangement for collecting light radiated from a light source and directing the light toward an object, the combination comprising:

wall means defining an elongated light-transparent member for receiving incident light from a light source substantially laterally surrounding at least a portion of said elongated light-transparent member in spaced apart relation thereto,

said wall means providing an interfacing surface for exposure to a light-transmissive medium,

said light-transparent member defined'by said wall means having an index of light refraction greater than the light-transmissive medium for enabling light passing through said light-transparent member to be reflected internally at the interfacingsun face provided by said wall means, and

said wall means further defining a substantially conical recess extending longitudinally in said elongated light-transparent member for causing light passing through said light-transparent member to be internally reflected in said elongated lighttransparent member. I

2. In a lamp arrangement according to claim 1, the combination further comprising a substantially conical reflector contiguous with the'substantially conical recess formed by said wall means for reflecting light passing through said light-transparent member.

3. In a lamp arrangement according to claim 2, said substantially conical recess having a configuration substantially equal to that generated by the revolution of a hypotenuse of a right triangle about an axis with one of the sides of the triangle being parallel to the axis of revolution wherein the sine of twice the angle between the hypotenuse and said one side of the triangle parallel to the axis of revolution equals the ratio of the index of refraction of the light transmissive medium to that of said light-transparent member.-

4. In a lamp arrangement according to claim 3, the combination further comprising reflector means surrounding laterally said light-transparent member in spaced-apart relation thereto for reflecting light from a light source toward said Light-transparent member.

5. A lamp arrangement, comprising:

a vapor tube light source having an envelope with substantially coaxial inner and outer tubular walls for containing a gaseous medium for producing light while serving as a conductor of electricity,

an elongated light transparent member located in the central axial opening of said coaxial tube for receiving laterally the light radiated internally from said gaseous discharge tube, said elongated light-transparent member being in spaced-apart relation to the inner tubular wall of said gaseous discharge tube and having an index of refraction greater than the index of refraction of a light-transmissive medium in the space between said elongated light-transparent member and said gaseous discharge tube, and

a reflective surface having a substantially conical configuration extending axially in said elongated light-transparent member and in optical contact therewith for reflecting light passing through said light-transparent member. 6. A lamp arrangement according to claim 5, wherein the combination further comprises:

cylindrical light reflector means surrounding the outer wall of said coaxial envelope for reflecting light from said coaxial envelope toward said elongated light-transparent member,

said cylindrical light reflector means being in contact with the gaseous medium contained in said coaxial envelope, and

said cylindrical light reflector means being electrically conductive and serving as an electrode during a gaseous discharge in said coaxial envelope.

7. [n a lamp arrangement according to claim 5, said substantially conical recess, having a configuration substantially equal to that generated by the revolution of a hypotenuse of a right triangle about an axis with one of the sides of the triangle parallel to the axis of revolution wherein the sine of'twice the angle between the hypotenuse and said one side of the triangle parallel to the axis of revolution equals the ratio of the index of refraction of the light transmissive medium to that of said light-transparent member.

8. ln a lamp arrangement, the combination comprising:

. light source means defining a vapor tube light source,

wall means defining an elongated light-transparent member for receiving light from said light source means,

said light source means substantially laterally surrounding at least a portion of said elongated lighttransparent member in spaced apart relation thereto, said wall means providing an interfacing surface for exposure to an adjacent light-transmissive medium,

said light-transparent member defined by said wall means having a greater index of light refraction than the surrounding medium for enabling light passing through said light-transparent member to be refracted at the interfacing surface provided by said wall means, and

a reflective surface having a substantially conical Y configuration extending axially in said elongated lighttransparent member and in optical contact therewith for reflecting light passing through said light-transparent member.

9. In a lamp arrangement according to claim 8, said substantially conical reflector having a configuration substantially equal to that generated by the revolution of a hypotenuse of a right triangle about an axis of revolution with one of the sides of the triangle being parallel to the axis of revolution wherein the sine of twice the angle between the hypotenuse and the side of the triangle parallel to the axis of revolution equals the ratio of the index of refraction of the light transmissive medium to that of said light-transparent member.

10. In a lamp arrangement according to claim 9, the combination further comprising:

an exterior light reflector surrounding said light source means,

said exterior light reflector being in contact with the vapor of said light source means, and

said exterior light reflector being electrically conductive and serving as an electrode for the vapor tube light source.

11. A reflector arrangement for a vapor tube light source having a circular configuration defining a central axial opening in which an elongated lighttransparent member is disposed for receiving light from the light source, the combination comprising:

an exterior light reflector having a cylindrical configuration and surrounding said circularly configured light source in coaxial relation therewith for reflecting light from said circularly configured light source toward the central axial opening defined by said light source, and

an interior light reflector having a substantially conical configuration and being located in the elongated light-transparent member in the central opening defined by said light source and in substantially coaxial alignment with said cylindrical light reflector for reflecting the light generally away from the central opening defined by said light source.

12. A reflector arrangement according to claim 11, wherein said exterior light reflector serves as an electrode for the vapor tube light source.

13. In a lamp arrangement, the combination comprisa vapor tube light source having an envelope with substantially coaxial inner and outer tubular walls for containing a gaseous medium suitable for producing light while serving as a conductor of electricity,

said inner tubular wall of said vapor tube light source defining a central axial opening in which light from said vaopr tube light source may be concentrated in an elongated light-transparent member disposed in the central axial opening for receiving the light from said light source,

an exterior light reflector having a cylindrical configuration surrounding the outer tubular wall of said vapor tube light source for reflecting light toward the central axial opening, and

a substantially conical reflector located in the elongated light-transparent member in the central axial opening defined by said inner tubular wall and in substantially coaxial alignment with said cylindrical light reflector for reflecting light from the central opening defined by said light source.

14. In a lamp arrangement according to claim 13, said exterior light reflector being constructed from an electrically conductive material and serving as an electrode for said vapor tube light source.

15. ln a lamp arrangement according to claim 13, said interior light reflector substantially blocking the passage of light through one end of the central axial opening defined by said inner tubular wall for causing the light radiation concentrated in the central axial opening to be directed toward the other end of the central axial opening. 

1. In a lamp arrangement for collecting light radiated from a light source and directing the light toward an object, the combination comprising: wall means defining an elongated light-transparent member for receiving incident light from a light source substantially laterally surrounding at least a portion of said elongated light-transparent member in spaced apart relation thereto, said wall means providing an interfacing surface for exposure to a light-transmissive medium, said light-transparent member defined by said wall means having an index of light refraction greater than the lighttransmissive medium for enabling light passing through said light-transparent member to be reflected internally at the interfacing surface provided by said wall means, and said wall means further defining a substantially conical recess extending longitudinally in said elongated light-transparent member for causing light passing through said light-transparent member to be internally reflected in said elongated lighttransparent member.
 2. In a lamp arrangement according to claim 1, the combination further comprising a substantially conical reflector contiguous with the substantially conical recess formed by said wall means for reflecting light passing through said light-transparent member.
 3. In a lamp arrangement according to claim 2, said substantially conical recess having a configuration substantially equal to that generated by the revolution of a hypotenuse of a right triangle about an axis with one of the sides of the triangle being parallel to the axis of revolution wherein the sine of twice the angle between the hypotenuse and said one side of the triangle parallel to the axis of revolution equals the ratio of the index of refraction of the light transmissive medium to that of said light-transparent member.
 4. In a lamp arrangement according to claim 3, the combination further comprising reflector means surrounding laterally said light-transparent member in spaced-apart relation thereto for reflecting light from a light source toward said Light-transparent member.
 5. A lamp arrangement, comprising: a vapor tube light source having an envelope with substantially coaxial inner and outer tubular walls for containing a gaseous medium for producing light while serving as a conductor of electricity, an elongated light transparent member located in the central axial opening of said coaxial tube for receiving laterally the light radiated internally from said gaseous discharge tube, said elongated light-transparent member being in spaced-apart relation to the inner tubular wall of said gaseous discharge tube and having an index of refraction greater than the index of refraction of a light-transmissive medium in the space between said elongated light-transparent member and said gaseous discharge tube, and a reflective surface having a substantially conical configuration extending axially in said elongated light-transparent member and in optical contact therewith for reflecting light passing through said light-transparent member.
 6. A lamp arrangement according to claim 5, wherein the combination further comprises: cylindrical light reflector means surrounding the outer wall of said coaxial envelope for reflecting light from said coaxial envelope toward said elongated light-transparent member, said cylindrical light reflector means being in contact with the gaseous medium contained in said coaxial envelope, and said cylindrical light reflector means being electrically conductive and serving as an electrode during a gaseous discharge in said coaxial envelope.
 7. In a lamp arrangement according to claim 5, said substantially conical recess, having a configuration substantially equal to that generated by the revolution of a hypotenuse of a right triangle about an axis with one of the sides of the triangle parallel to the axis of revolution wherein the sine of twice the angle between the hypotenuse and said one side of the triangle parallel to the axis of revolution equals the ratio of the index of refraction of the light transmissive medium to that of said light-transparent member.
 8. In a lamp arrangement, the combination comprising: light source means defining a vapor tube light source, wall means defining an elongated light-transparent member for receiving light from said light source means, said light source means substantially laterally surrounding at least a portion of said elongated light-transparent member in spaced apart relation thereto, said wall means providing an interfacing surface for exposure to an adjacent light-transmissive medium, said light-transparent member defined by said wall means having a greater index of light refraction than the surrounding medium for enabling light passing through said light-transparent member to be refracted at the interfacing surface provided by said wall means, and a reflective surface having a substantially conical configuration extending axially in said elongated light-transparent member and in optical contact therewith for reflecting light passing through said light-transparent member.
 9. In a lamp arrangement according to claim 8, said substantially conical reflector having a configuration substantially equal to that generated by the revolution of a hypotenuse of a right triangle about an axis of revolution with one of the sides of the triangle being parallel to the axis of revolution wherein the sine of twice the angle between the hypotenuse and the side of the triangle parallel to the axis of revolution equals the ratio of the index of refraction of the light transmissive medium to that of said light-transparent member.
 10. In a lamp arrangement according to claim 9, the combination further comprising: an exterior light reflector surrounding said light source means, said exterior light reflector being in contact with the vapor of said light source means, and said exterior light reflector being electrically conductive and serving as an electrode for the vapor tube light source.
 11. A reflector arrangement for a vapor tube light source having a circular configuration defining a central axial opening in which an elongated light-transparent member is disposed for receiving light from the light source, the combination comprising: an exterior light reflector having a cylindrical configuration and surrounding said circularly configured light source in coaxial relation therewith for reflecting light from said circularly configured light source toward the central axial opening defined by said light source, and an interior light reflector having a substantially conical configuration and being located in the elongated light-transparent member in the central opening defined by said light source and in substantially coaxial alignment with said cylindrical light reflector for reflecting the light generally away from the central opening defined by said light source.
 12. A reflector arrangement according to claim 11, wherein said exterior light reflector serves as an electrode for the vapor tube light source. Pg,19
 13. In a lamp arrangement, the combination comprising: a vapor tube light source having an envelope with substantially coaxial inner and outer tubular walls for containing a gaseous medium suitable for producing light while serving as a conductor of electricity, said inner tubular wall of said vapor tube light source defining a central axial opening in which light from said vaopr tube light source may be concentrated in an elongated light-transparent member disposed in the central axial opening for receiving the light from said light source, an exterior light reflector having a cylindrical configuration surrounding the outer tubular wall of said vapor tube light source for reflecting light toward the central axial opening, and a substantially conical reflector located in the elongated light-transparent member in the central axial opening defined by said inner tubular wall and in substantially coaxial alignment with said cylindrical light reflector for reflecting light from the central opening defined by said light source.
 14. In a lamp arrangement according to claim 13, said exterior light reflector being constructed from an electrically conductive material and serving as an electrode for said vapor tube light source.
 15. In a lamp arrangement according to claim 13, said interior light reflector substantially blocking the passage of light through one end of the central axial opening defined by said inner tubular wall for causing the light radiation concentrated in the central axial opening to be directed toward the other end of the central axial opening. 